Revolving tube furnace



April 18, 1933. H. SCHULTZE REVOLVING TUBE FURNACE Filed June 15, 1929[rm/211K07- Hermann SchuZZzc By W Patented Apr. 18, 1933 UNITED STATESPATENT OFFICE HERMANN SCHULTZE, OF FRANKFORT-ON-THE-MAIN-GBIESHEIM,GERMANY, AS-

SIGNOB TO I. G. FARBENINDUSTRIE AKTIE-NG-ESELLSGHAFT, OF FRANKFORT-ON-THE-MAIN, GERMANY, A CORPORATION OF GER-MALT! I i REVOLVING TUBEnu'nnncn Application filed June 13, 1929, Serial No. 370,567, and inGermany May 2, 1927.

I have filed application in Germany on May 2, 1927.

My present invention relates to a revolving cylinder furnace of which Iintend to make use especially in performing the production of sodiumsulfate according to Hargreaves process which comprises acting in theheat u on sodium chloride with S0 steam and su icient air to ensure aquantity of oxygen in the gases at least sufficient for oxidizing S0 toS0 Attempts have been made to improve the Hargreaves process byeffecting the reaction in revolving furnaces. However, all suchproposals have failed to provide an unobjectionable result.

Now, my experiments have demonstrated that a satisfactory result isdependent on certain conditions which hitherto were not sufiicientlyrecognized. The most important of these conditions are the following:

(1) It is necessary to employ porous lumps or bricks of sodium chlorideeven in revolving furnace work.

(2) The pieces of salt must be of small dimensions in order that thegases may penetrate easily and quickly into the innermost parts thereof.

(3) A steady supply of gas and the maintenance of a uniform temperaturemust be ensured by accurate regulation, so as to avoid agglomeration orcaking of salt ensuing from local overheating, to which the failure ofprior experiments was principally due.

(4) The inclusion of incompletely formed sulfate (due to some of thelumps getting ahead of the others during their passage through thefurnace) should be prevented by accurately controlling the travel of thesalt through the furnace.

Consequently, the revolving furnace must be so designed as to ensure theperfectly controlled and undisturbed counterflow between the solid andgaseous constituents of the reaction, and that the salt bricks areuniformly conveyed, without endangering their shape and with a minimumof relative displacement.

The invention will hereinafter be more fully described with reference tothe accompanying drawing which illustrates diagrammatically a revolvingtube-furnace suitable for carrying the herein described method 1ntopractical effect.

Fig. l is a longitudinal section of the furnace, Fig. 2 is a sectionalong line 22 of Fig. 1. The same reference characters are used in bothfigures to indicate the same parts.

In said drawing A denotes a revolving cyl nder which is completelytraversed by an axially disposed hollow shaft B round which is mounted ahelix C, the inner rim of which is secured to-the said hollow shaft B,whereas its outer edge extends'as closely as possible towards the innerwall of the revolving cylinder A. Adjoining to one end of the cylinder Aand suitably packed is arranged a stationary head member D, pro videdwith a feed hopper E for the salt pieces, together with a gas outletpipe F and gas intake connection K leading to the hollow shaft B. At theother end is a cap or closure G connected with a double valve chamberthrough which the finished product is discharged into a receiver forremoval. For the greater portion of its length the hollow shaft B servesas a preheater for the reaction gases (8C air, and steam) introduced atthe head end through K, which gases are then allowed to issue throughopenings H, the hollow shaft B being closed behind the holes H, into thefurnace chamber A. Then the gases pass in reversed direction of flow andin countercurrent to the salt pieces backward to the head member Dfollowing the helical path along hollow shaft B passing over the charge00 disposed in A (not shown in the drawing), whose quantity is notsufficient to contact hollow shaft B, while A is rotating.

In Fig. 2 the disposition of the charge a; during working is shown.

At the head end, the gases are finally withdrawn through the outlet F,for conveyance to the hydrochloric acid absorption plant.

For the purpose of heating up, and also for regulating the temperaturewhen required, the revolving cylinder A is provided with an electricresistance heater, divided into sections J each of which can be set inaction according to the internal temperature attained. Should theshutting off of the heating current no longer suflice to lower thetemperature of the exothermic reaction to a sufficient extent,detachable portions L of the heat insulating jacket may be removed oneafter the other. The regulation of the temperature in the furnace mayalso be effected by varying the temperature of the mixture of S0 air,and steam.

Throughout the entire zone of contact between the salt bricks and thesulfurous gases, the temperature is kept at approximately 520 0., but inany case above 460 0., so as to prevent caking due to the formation ofbisulfate. After the hot salt bricks have passed over into a zone freefrom S0 gas (behind H), the final product is cooled having retained itssmall grained form by being guided ata slow rate in the turns of thehelix C, and the sulfate is discharged, into the air or other inertgases, by means of the double valve chamber behind the cap G.

I claim:

In a revolving furnace, in combination, a revolving cylinder, astationary hollow shaft located in the cylinder and provided with anouter helix attached to the shaft along its total length having adiameter nearly equal to that of the revolving cylinder, an inlet at oneend of said shaft for introducing reaction gases into the latter, anoutlet for gas in said shaft at a distance from said inlet of more thanhalf the length of said shaft, and an outlet for gas on said revolvingcylinder at the same end Where the gas inlet is provided on the shaft.

In testimony whereof I have hereunto set my hand.

HERMANN SCHULTZE.

